In the above-noted U.S. Pat. No. 4,838,855 by one of the co-inventors hereof, there is disclosed an aspiration system for supplying fluid to and withdrawing undiluted blood from tubing connected to the blood vessel of a patient, for example, by an in-dwelling catheter, without opening the tubing system to atmosphere. In that system, a proximal section of tubing is placed in communication with a source of fluid under pressure, for example, intravenous fluid. The proximal tubing section extends to a two-way valve, which in turn is connected to an intermediate tubing section. The intermediate tubing section is connected to an aspirator receiver, in turn connected to distal tubing coupled to the in-dwelling catheter. In one position of the valve, the intermediate tubing section is connected with a fluid reservoir and in the other position of the valve, the intermediate tubing section is coupled with the source of fluid under pressure. The aspirator receiver includes a housing having a flow channel and a passage in communication with the flow channel and occluded by a septum. The septum is formed of resilient material such that a needle may penetrate the septum to withdraw blood from the flow channel and, upon withdrawal of the needle, the septum is self-sealing.
In that system, the fluid reservoir has a volume sufficient such that, when the valve is opened to afford communication between the reservoir and the intermediate and distal tubing sections and is closed to the source of fluid under pressure, sufficient resident fluid in those tubing sections can be withdrawn into the reservoir so that the aspirator receiver is filled with undiluted blood from the in-dwelling catheter through the distal tubing into the aspirator receiver flow channel. When the reservoir is full, a needle forming part of a syringe, may be inserted through the septum of the aspirator receiver and into communication with the blood in the flow channel. The undiluted blood under pressure thus fills the syringe. Once a satisfactory sample has been obtained, the syringe needle may be withdrawn from the aspirator receiver septum which automatically reseals. Pressure is then applied to the fluid temporarily resident in the reservoir to return such fluid to the tubing sections without loss of blood other than that actually removed for testing. Indeed, measurements can be made without any loss of blood by interfacing the blood analysis section directly with blood analysis sensors or membranes.
In our prior U.S. Pat. No. 5,178,607, there are also disclosed certain improvements in the above-described system, including a blunt cannula or needle for use with a preperforated septum. As explained in that application, the use of a blunt cannula or needle prevents accidental needlesticks typically associated with inserting a needle through septa or, more generally, when using unprotected needles. The blunt needle is thus used in connection with a preperforated septum which is also self-sealing. The tip of the blunt needle enables the force required to pass the tip of the blunt needle into the septum to be considerably less than the force required to penetrate the surface of normal intact human skin of the hand or arms whereby accidental misdirection of the blunt needle tip against the skin will not result in penetration of the skin. Hence, the risk of needlestick while obtaining blood sample through the septum is virtually eliminated.
In our U.S. Pat. No. 5,114,400 an improvement with respect to the two systems previously described is disclosed which eliminates the problem of blood spurting from the cannula tip when the cannula is removed from the septum of the aspirator receiver. The syringe typically has a bubble of air trapped within its interior chamber. The elevated pressure within the flow channel when the cannula is inserted through the septum positively pressurizes the syringe during sampling, compressing that air bubble. Upon removal of the cannula, the opening at the tip of the cannula is exposed to the lower atmospheric pressure, thus causing the pressurized air bubble within the syringe to expand and the blood to undesirably spurt from the tip of the cannula.
In U.S. Pat. No. 5,114,400 that blood spurting problem is cured by enabling depressurization of the air bubble within the syringe while the cannula tip is occluded from fluid communication with the pressurized blood vessel. Although other means to occlude such fluid communication are included in the teaching, the preferred embodiment discloses the use of the septum to occlude the cannula near its tip. Particularly, a shroud is provided about the blunt cannula which, in cooperation with the aspirator receiver housing, indicates when the tip of the cannula is occluded within the septum during withdrawal of the cannula from the septum. Such occlusion indicator preferably includes cooperating detents on the aspirator receiver housing and the shroud affording sensory perception of the occlusion. When those detents engage, the sensory, e.g., tactile indication afforded thereby, permits the nurse to temporarily stop withdrawing the cannula from the aspirator receiver housing and to retract the syringe piston. This induces a negative pressure in the syringe barrel, enabling expansion of the trapped air bubble within the syringe. Upon full withdrawal of the cannula, the atmospheric pressure is at least equal to or greater than the pressure within the syringe thus eliminating the blood spurting problem.
Notwithstanding these various improvements in blood aspiration assemblies, there remains a significant problem in transferring the blood sample from the aforementioned syringe to another container, for example, the standard adult vacuum-filled container. A container of this type typically comprises a cylindrical glass or plastic tube closed at one end. Its opposite open end is normally occluded by a septum, i.e., a rubber stopper. Typically, a practitioner would penetrate the septum of the aspirator receiver with the needle of a conventional syringe, withdraw the needle once an adequate volume of blood had been withdrawn into the syringe, and then attempt to direct the needle tip for penetration through the septum of the vacuum container. Obviously, using that procedure, there is substantial danger of accidental needlestick during insertion of the needle of the syringe into the septum of the aspirator receiver, its withdrawal from that septum, movement of the syringe to the vacuum container, and attempted penetration of the rubber septum of the container.
This problem has been recognized and a very complex solution to the problem has been offered. Particularly, a blood protection system has been developed which is illustrated in FIGS. 10 and 11 hereof. That system includes a sampling syringe S (FIG. 6) having a shrouded cannula C. The shrouded cannula is applied to the septum of an aspirator receiver R of an aspiration system AS to withdraw a blood sample. The cannula C is then removed from the aspirator receiver housing. The cannula, however, is too blunt to penetrate the septum 146, usually formed of rubber or like material, of the vacuum-filled container 148 to effect direct transfer of the blood sample to the container. Moreover, the shroud about the cannula does not match the septum on the standard adult vacuum-filled container C (FIG. 11). This system thus employs an intermediate blood transfer unit BTU which includes a bore at one end occluded by a septum 150 penetrable by the shrouded blunt cannula C. At the opposite end, there is provided an elongated cylindrical chamber 152 open at one end for receiving the vacuum-filled container C, septum end first. The container is advanced within this chamber such that a needle 154 forming part of the blood transfer unit may penetrate the septum of the vacuum container 148. The needle 154 is in communication with the bore at the opposite end of the blood transfer unit. When the container 148 and sampling syringe S are connected to the blood transfer unit, blood is then transferred from the sampling syringe S through its blunt cannula C, and through the septum 150 and bore at one end of the blood transfer unit BTU and then through the needle 154 of the blood transfer unit through the septum of the vacuum container for reception within the container. Direct transfer of blood from the sampling syringe S to the container 148 in that system is not possible because the blunt cannula C is not sufficiently sharp to penetrate the septum 146 of the vacuum-filled container 148. Also, the shroud 156 of the sampling syringe is too small to accommodate the septum of the vacuum-filled container.
According to the present invention, there is provided apparatus and methods for transferring blood between the aspirator receiver of a blood aspiration system and a standard adult vacuum-filled container which minimizes problems associated with needlesticks and consequent transmittal of infectious diseases and the need for any intermediate blood transfer unit. In accordance with the present invention, there is provided an aspirator having at one end a cannula extending within, but radially spaced from, a surrounding shroud. The tip of the cannula is blunt yet sufficiently sharp to penetrate the septum of a standard vacuum-filled container. Direct transfer of the blood sample from the aspirator to the vacuum container is accomplished by (i) forming the septum of the aspirator receiver housing (including any surrounding portion of the housing) substantially identical in shape and dimension to the septum of the standard adult vacuum-filled container; and (ii) forming the interior of the shroud complementary to both the septum of the aspirator receiver housing (including any surrounding portion of the housing) and the septum of the standard adult vacuum-filled container. Further, the shroud extends distally beyond the tip of the cannula. While thus recessed from the end of the shroud, the cannula is exposed to engagement by an individual's finger inserted within the open end of the shroud because the interior diameter required to receive an adult vacutainer is larger than the adult human finger. The tip of the cannula is therefore formed sufficiently blunt to prevent penetration of intact human skin on an individual's hands and arms even upon application of casual inadvertent force.
To facilitate the transfer of the blood sample from the aspiration system to the vacuum-filled container, the aspirator includes an interior chamber or receptacle in communication with the bore of the cannula for receiving blood from the flow channel of the aspirator receiver through the cannula. The interior chamber can include a plunger for displacing the blood sample into the vacuum-filled container when the aspirator and container are connected.
Preferably, the end of the aspirator receiver housing having the passage occluded by the septum is substantially identical in shape and dimension to the end of the vacuum-filled container including its septum. Particularly, the aspirator receiver housing and vacuum-filled container ends are preferably cylindrical, similar or identical in diameter and complementary in diameter to the internal diameter of the preferably cylindrically-shaped shroud surrounding the cannula. In this manner, the aspirator may be centered over the septum of the aspirator receiver housing by engagement of the shroud about the housing end or septum to enable substantial coaxial penetration of the septum, preferably through a perforation in the septum. Penetration may therefore proceed without danger of breaking the cannula by canting it relative to the housing. Upon receipt of the blood sample within its interior chamber, the aspirator may be withdrawn from the aspirator receiver housing, preferably using the aspirator occlusion indicator of the previously mentioned application, to avoid the problem of blood spurting from the cannula tip upon complete removal of the aspirator. Once removed, the aspirator may be similarly centered upon the stopper of the vacuum-filled container by engagement of the shroud about the stopper. The blunt cannula is sufficiently sharp to penetrate the stopper of the vacuum-filled container without preperforating the septum. The plunger of the aspirator may then be actuated to facilitate displacement of the blood sample from the aspirator directly into the container. Upon separation of the aspirator and container, the stopper of the vacuum-filled container automatically seals.
In a preferred embodiment according to the present invention, there is provided, in combination with a blood aspiration system connected to a pressure transducer and a discrete container, an apparatus for transferring a sample of blood from the aspiration system to the discrete container comprising an aspirator including an axially extending cannula having a distal tip, the cannula having a bore with first and second openings adjacent opposite ends of the bore and a shroud extending about the cannula in transversely spaced relation thereto, the shroud extending axially beyond the distal tip of the cannula, an aspiration receiver which forms part of the blood aspiration system and which includes a housing having a flow channel for communication with the human vasculature for flowing blood through the flow channel, the housing having a portion for receiving the cannula to locate the first opening of the cannula in communication with the flow channel. Blood receiving means are coupled to the aspirator in communication with the second opening for receiving blood. The discrete container has an opening at one end and a stopper occluding the opening, the external configurations of the one end of the container and the housing receiving portion, respectively, being complementary to the internal configuration of the shroud whereby, (i) upon application of the aspirator to the aspirator receiver, the shroud engages about the housing receiving portion and centers the cannula for penetration of the housing receiving portion to locate the first opening in communication with the flow channel and thereby to communicate blood from the flow channel through the bore into the blood receiving means, and, (ii) upon removal of the aspirator from the aspirator receiver and upon application of the aspirator to the container, the shroud engages about the container end and centers the cannula for penetration through the septum of the container to locate the first opening in communication with the container and thereby to communicate blood from the receiving means through the bore into the container.
In a further preferred embodiment according to the present invention, there is provided apparatus for transferring a sample of blood from a flow channel in fluid communication with an aspirator receiver to a discrete container closed at one end by a stopper, the flow channel being adapted for communication with the lumen of a blood vessel of a patient and a passage of the aspirator receiver opening through an aspirator receiver portion having a predetermined outside diameter and which passage is occluded by a septum, comprising an aspirator including an axially extending cannula having a distal tip, a first opening adjacent the tip for receiving blood from the flow channel upon penetration of the septum by the cannula, a second opening and a bore through the cannula extending between the first and second openings, the cannula being adapted for connection to a receptacle for communicating blood received through the first opening into the bore and through the second opening into the receptacle and a generally cylindrical shroud extending about the cannula in radially spaced relation thereto and extending distally axially beyond the distal tip of the cannula, the internal diameter of the shroud being at least as great as about 17.5 mm for successively receiving the aspirator receiver portion and the ends of the container enabling transfer of blood directly from the aspirator receiver to the receptacle and from the receptacle directly through the cannula to the container.
In a further preferred embodiment according to the present invention, there is provided a method of transferring a sample of blood from a flow channel in an aspirator receiver of an aspiration system to a discrete container having a septum closing one end thereof wherein the flow channel is adapted for communication with the lumen of a blood vessel of a patient and the aspirator receiver has a housing portion for receiving a cannula, comprising the steps of providing a flow of blood from the patient into the flow channel, positively centering the cannula of the aspirator relative to the housing receiving portion by engaging a shroud on the aspirator about the housing receiving portion, penetrating the housing receiving portion with the centered cannula to place the cannula in communication with the blood in the flow channel, flowing blood from the flow channel through the cannula for reception in a receptacle in communication with the cannula, removing the aspirator from the aspirator receiver, positively centering the cannula relative to the septum of the container by engaging the shroud of the aspirator about the end of the container, penetrating the septum of the container with the centered cannula to place the container in communication with the blood in the receptacle and flowing blood from the receptacle into the container.
It is therefore a primary object of the present invention to provide apparatus and methods for the direct transfer of a blood sample from a blood aspirator assembly to an adult vacuum-filled container without injury from needlesticks, in a manner achieving a centering of the cannula relative to the septa thereby avoiding breaking the cannula, and without the need for any intermediate blood transfer unit.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.